1. Field of the Invention
The present invention relates to a helical scan type magnetic recording and reproducing apparatus for recording and reproducing an analog video signal and a digital video signal.
2. Description of the Prior Art
When an NTSC signal and a PAL signal which are digitized in corresponding digital video tape recorders (referred to as "VTR's", hereinafter) are recorded in the same number of tracks on a magnetic tape per video signal frame, it is necessary in the conventional technology to change the recording density of the magnetic tape between the NTSC system and the PAL system and, therefore, it is necessary to provide two separate systems each including a recording circuit and a reproducing circuit. In order to solve this problem, the format of a track and the rotation speed of a drum in case of recording of the NTSC signal are made substantially equal to those in a case of recording of the PAL signal by setting the number of tracks per NTSC video signal frame and the number of tracks per PAL video signal 5: 6. Digital VTR's using this system are known and practiced as those of the so-called D1 and D3 standards.
On the other hand, a system is disclosed in Japanese Patent Application Laid-open No. H5-207507 in which, in recording a digital signal, the rotation speed of drum is made twice that of an analog video signal recording.
In such digital VTR of D1 or D3 standard, the rotation speed which is twice that of the analog video signal recording is as high as 9000 r.p.m. or 4500 r.p.m. which requires a dedicated rotary drum. That is, a rotary drum of a home use VTR which rotates at 1800 r.p.m. (for PAL or SECAM system, 1500 r.p.m. can not be used and the construction of the VTR itself becomes complicated.
Further, in the system in which the rotation speed of the rotary drum is recorded is made twice in order to record a digital signal, the tape format must be changed between the NTSC and PAL (or SECAM) signals and editing by the frame is impossible.